At the rally, Biden painted Nolan as a man who, like him, knows the middle class and represents it, Roll Call reported. Some working-class Democrats on the Iron Range – which has coped with huge job cuts in the mining industry in recent years –have drifted toward Republican Donald Trump's message.

Biden's goal is to keep those Democrats (and people on the fence) voting for Nolan, Roll Call said.

And because the Nolan-Mills race was so close last time around, Republicans see the district as possible to flip. That's led to some of the highest outside spending of any U.S. House race this cycle, MinnPost said.

When Nolan won in 2014, he ousted a one-term Republican, Chip Cravaack. But prior to that, Democrat Jim Oberstar held the seat for more than 30 years.

There are currently 246 Republicans and 186 Democrats in the U.S. House – Minnesota has three of those Republicans (in the 2nd, 3rd and 6th districts), and five Democrats (in the 1st, 4th, 5th, 7th and 8th).

To find news, commentary, and local events leading up to the 2016 election, head to Go Vote MN.